abstract

This paper introduces an innovative design concept for a low-cost solar-thermal aeration system for fish ponds which is amenable to implementation in resource-constrained settings. In its most basic form, the system consists of a metallic solar thermal collector and a heat transfer column (referred to as conduction element in this paper), which induces convective circulation by dissipating heat to the cooler, deeper layers of the pond. As a result of the circulation, oxygen generated by phytoplankton at the top of the pond is distributed throughout the water column, preventing oxygen losses to the atmosphere due to surface supersaturation and increasing the overall dissolved oxygen (DO) content in the pond. This paper presents a design study to evaluate different system configurations. Thermofluidic numerical models were implemented to systematically analyze and compare the mass flow rate through the draft tube induced by convection. Furthermore, parametric studies were performed to evaluate the effect of the insulation patch length and the aluminum plate thickness on the overall performance of the device (i.e. the induced mass flow rate through the draft tube). It was found that the two-fin configuration with split conduction elements was superior to the central rod design in terms of performance. In addition, it was found that depending on the insulation patch length, the induced mass flow rates can be increased up to 5 times. The results from the computational models indicate that the device can induce the convective circulation in order to improve the DO content at deep levels of the ponds and has potential to improve aquaculture productivity in resource-constrained settings. The results from this study will be used to configure systems for future field evaluations that will be performed in fish ponds in Bangladesh.

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